Float-type flow meters are frequently used to measure the flow of air, industrial gases or other fluids. In flow meters of this type, a float is mounted for movement within a tapered passage in the body of the meter and the float will rise in proportion to the rate of gas flow. The float carries a rod which extends downwardly into an elongated guard that houses a sight glass. An indicator mounted on the lower end of the rod moves within sight glass in accordance with movement of the float and indicates the rate of gas flow on a calibrated scale that is mounted on the guard adjacent the sight glass.
If the flow meter is subjected to extreme high or sudden surge pressure conditions, as could occur in the event of a malfunction of the pressure regulator or by the normal sudden opening of a solenoid valve in the fluid line, the high or sudden pressure could fracture the sight glass. Therefore, it is desirable to provide a protective shield around the sight glass to prevent glass fragments from dispersing into the surrounding atmosphere in the event of fracture.
In addition, the scale and sight glass on an industrial-type flow meter may become contaminated with dirt, oil and other foreign material making it difficult to read the rate of flow, and in certain instances it is difficult to adequately remove the contamination from the sight glass and scale.